Apparatus and method to remove animal waste from litter

ABSTRACT

An apparatus and method for separating animal waste from litter are provided. In one form, the apparatus includes a drum that contains litter and a helical rake that is rotatable in the drum. The rake can rotate relative to the drum to reduce power requirements for the rotary rake drive. Preferably, the drum is also rotatable by turning of the rake in the drum, but only for a limited, fixed angular distance which also reduces peak power requirements for the rotary drive motor for the rake.

FIELD OF THE INVENTION

The invention relates to a litter receptacle for holding animal waste,and in particular, a self-cleaning litter receptacle and method ofremoving animal waste from a litter receptacle.

BACKGROUND OF THE INVENTION

Conventional self-cleaning litter receptacles usually are open-top boxesthat hold granular litter. Some litter boxes automatically remove animalwaste from the litter, typically by using a motor to drive a siftingstructure, such as a rake or scoop, through the litter to separate thewaste from the litter. The motor must provide enough power to overcomethe weight and agglomeration (i.e., adherence between litter grains) ofthe litter to push the rake through the litter, especially when startingthe motion of the rake.

Prior self-cleaning litter receptacles can also take the form of a drumor other enclosure that holds the litter. For instance, U.S. Pat. No.5,048,464, issued to Shirley, and U.S. Pat. No. 6,286,457, issued toSugahara, both disclose a litter box with a motor that drives a drum forrotation that, in turn, rotates a helical-shaped screen or spiral filterattached to the sides of the drum for sifting through the litter. Use ofa drum is advantageous because the drum keeps litter from escaping thelitter box while it is rotating, and minimizes the unpleasant odors thatemanate from typical open-top litter boxes. A rotating drum or cylinder,however, increases the power requirements of the motor because the motoris required to power the entire weight of the drum or other bulkyenclosure for rotation as well as having to overcome the weight of thelitter and waste contained therein.

Since the motor can be the most expensive component in the entiresystem, a self-cleaning litter receptacle that minimizes the powerrequirements of the motor while still sufficiently separating the animalwaste from the litter would be desirable.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a generally cylindricalenclosure is provided for containing litter, and a separating devicesuch as a helical rake is disposed in the cylindrical enclosure forseparating animal waste from the litter in the enclosure. Rather thanrotating the cylindrical enclosure, a rotary drive is provided thatrotates the separating device to move relative to the enclosure andlitter therein. Since the relatively heavy weight of the cylindricalenclosure and litter need not be constantly rotated by the rotary drive,the power requirements therefor can be kept to a minimum.

In accordance with another aspect of the invention, a litter receptacleis provided, and a sifting member is driven through the litter in thereceptacle. A support for the receptacle allows the receptacle to movedue to the sifting member being driven through litter in the receptacle.Accordingly, when the sifting member initially encounters agglomeratesstuck to the receptacle surface, it does not have to completely separatethe agglomerates before it can continue to be driven through the littersince the receptacle and stuck agglomerates can move with the siftingmember. In other words, the drive force applied to the sifting memberneed not be so large that it initially has to overcome the frictionalforce between the sticky agglomerates and the receptacle since thereceptacle is supported for movement in the direction the sifting memberis driven. Rather, in a preferred form, the receptacle is provided witha predetermined amount of movement before a stop acts to cease continuedmovement of the receptacle. However, at this point, the drive hasalready started shifting the sifting member so that any stuckagglomerates at the sifting member have inertia forces associatedtherewith that will assist in dislodging them from the receptacle,unlike the situation at start-up of the sifting member drive.

In a preferred form of the invention, a cylindrical drum and a helicalrake in the drum are provided. The drum is rotatably mounted via arotary support such as rotary bearings or the like, and a rotary drivedrives the helical rake for rotation in the drum. A stop is arranged sothat the drum rotates by only a predetermined, limited amount, e.g.,about 20 to about 180 degrees. Preferably, the drum rotates about 25degrees. The limited rotation amount afforded the drum keeps powerrequirements for the rotary drive to a minimum, particularly at start-upwhen frictional forces between the sticky agglomerates and the innerdrum surface will typically be at their highest.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, front perspective view of an apparatus forremoving animal waste from a quantity of litter in accordance with thepresent invention showing a cylindrical drum in which litter iscontained;

FIG. 2 is a partially exploded, rear, perspective view of the apparatusof FIG. 1 showing a storage container for receipt of animal waste fromthe drum;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2 showinga helical sifting member within the chamber;

FIG. 4 is an enlarged view taken along line 4-4 of FIG. 3 showing theconstruction of the sifting member;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 3 showinga direct drive transmission between a motor and the sifting member;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 3 showinga rear wall of the drum and an opening therein for removing the animalwaste from the chamber.

FIG. 6A is a enlarged view from FIG. 6 showing a stop formed between thedrum and an outer stationary housing;

FIGS. 7A-11B are side and corresponding end cross-sectional views of theinterior of the drum showing various stages of a cleaning cycle with thesifting member removing animal waste from the chamber;

FIG. 12 is a flowchart of exemplary methods of removing animal wasteusing the apparatus of FIG. 1; and

FIG. 13 is a perspective view of an alternative storage chamber for usewith the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an apparatus 10 for removing animal waste 12deposited in a quantity of litter 14 is illustrated. The illustratedapparatus 10 includes a base 16 and a litter receptacle 18, preferablyan enclosure such as a cylindrical drum, mounted on the base 16. As usedherein, the animal waste 12 may include any bodily excretions whetherliquid or solid that may be deposited in the litter 14. The waste 12 maybe just the waste itself, or may be the animal waste 12 combined withthe litter 14, such as when liquid and solid waste matter combines withthe litter to form a clumped mass of waste and litter agglomerates.

The preferred and illustrated cylindrical drum receptacle or enclosure18 includes a generally cylindrical side wall 19 extending betweenopposing front and rear end walls 20 and 22, respectively. The drum 18has an internal chamber 24 formed by the walls 19, 20, and 22 and inwhich the litter 14 is contained, generally at the bottom thereof. Aseparating device 26 is provided in the chamber 24 for separating theanimal waste 12 from the litter 14 when moved through the litter 14 inthe chamber 24. The separating device 26 can be a sifting member, suchas a helical rake, that is driven by a rotary drive 28, such as a motor,connected to the separating device 26.

In order to minimize the size or power requirements of the rotary drive28, the separating device 26 is turned or rotated relative to the drum18. That is, the drive 28 moves the separating device relative to theenclosure or receptacle 18, which in the illustrated form is acylindrical drum, but other configurations for the receptacle 18 couldalso be employed. In this manner, the rotary drive 28 generally does notneed to rotate the relatively heavy weight of the drum 18 and litter 14contained therein. The rotary drive 28, therefore, has a reduced peakpower or maximum horse power/torque rating that is significantly lessthan what would be needed to continuously rotate the drum 18, separatingdevice 26, and litter 14 at the same time.

The drum 18 is also rotatably mounted to the base 16 such that the drum18 can rotate as an incident of rotation of the rake 26 therein for aninitial, limited angular amount. Preferably, the drum 18 is free torotate on the base 16 about a longitudinal axis Z (FIG. 3) from itsinitial start-up, rest position for a distance of about 20 to about 180degrees. Preferably, the drum rotates less than about 90 degrees, suchas about 25 degrees. To that end, support 38 is provided that allows thedrum 18 to rotate for the limited angular distance as a result of theseparating device 26 being moved or shifted through the litter 14. Thatis, while the rotary drive 28 directly rotates the separating device 26(as more fully described below), an interference or engagement betweenthe separating device 26 and the litter 14 and/ or the stuck animalwaste 12 may cause the drum 18 to rotate along with the separatingdevice 26 about the support 38. Further, the helical rake 26 may bedisposed in the drum chamber 24 such that a radially outer edge 76 ofthe rake 26 is closely adjacent to or in scraping engagement with theinner surface 60 of the cylindrical drum wall 19. If in engagement withthe wall 19, rotation of the rake 26 in the drum 18 may also generatelimited rotation of the drum 18, if the strength of the frictionalforces therebetween are greater than that of forces tending to overcomethese frictional forces such as the weight of the drum 18 and littertherein. Such drum rotation may also occur with the scraping edge 76closely spaced to the wall 19. The drum 18, therefore, may be indirectlyrotated by the rotary drive 28 via rotation of the separating device 26.Such configuration is advantageous in keeping the power requirements forthe rotary drive 28 to a minimum because the rotary drive 28 also doesnot need to overcome any large, initial frictional or adherent forcesbetween the drum 18, litter 14, and/or animal waste 12 as may beencountered if the separation device 26 was moved in a fixed receptacle.In addition to being less costly to purchase, such smaller rotary drive28 is advantageous in that the device 28 weighs less, is quieter, and ismore cost efficient to operate.

In this manner, the rotary drive 28 does not need to overcome the fullfrictional or adherent forces that typically will form between the drumside wall 19 and agglomerates of animal waste 12 and litter 14 that maybe stuck to drum inner surface 60. It should also be noted that the rake26 and drum 18 need not rotate together in precision at the same rate.Instead, it is conceivable that the rake 26 can rotate faster than thedrum 18 even though the drum 18 is also being rotated by rotation of therake 26 therein. In this instance, the rake 26 may be encounteringpockets of frictional resistance at different locations in the litter 14that it overcomes as it is driven therethrough so that the drum 18 maynot rotate in synch with the rotation of the rake but may stop or slowdown occasionally depending on the frictional forces the rake 26 isencountering at any one time during its rotation through the litter. Inany event, at no time will the point 104 b located at the bottommostposition at the initial, rest position of the drum 18 rotate beyond thelimited angular amount, e.g., 90 degrees, as previously mentioned and aswill be described more fully hereafter. The present apparatus 10 takesadvantage of these frictional forces so that the rotary drive forceapplied to the rake 26 is transmitted to the drum 18 at the innersurface 60 therebetween. In this manner, the drum 18 can rotate with therake 26 for the limited angular distance, as previously described. Whenthe rotary drive force exceeds the frictional force, generally the rakeand drum will no longer rotate together. As a result, it is believedthat the peak power requirements of the rotary motor drive 28 can bemaintained at about less than half of that required by a configurationthat uses a rotating or otherwise moving sifting member in a fixed,non-rotating drum or other enclosure.

With such configuration, the apparatus 10 only needs a very small rotarydrive 28. For example, a small 6 volt DC gear-drive motor that canoperate on D-cell batteries (i.e., about 6 D-Cell batteries) or asuitable wall transformer that converts AC to DC power (i.e., a 115 VoltAC to 6 volt DC converter). In such form, the rotary drive 28 preferablyhas less than about 0.1 horsepower, and most preferably about 1/50horsepower. Such a motor is suitable to rotate the rake 26 within thedrum 18 at about 2 RPM.

As mentioned above, any concurrent rotation between the drum 18 and theseparating device 26 may cease when the separating device 26 exceeds theopposite forces of the litter 14 and the drum wall 19, such asfrictional, adherent, or gravitational forces. These forces may beexceeded, in one instance, upon shifting of the litter 14 within thechamber 24. For example, upon sufficient rotation of the drum 18, thelitter 14 therewithin may shift or move in the chamber 24 due togravity. Upon sufficient shifting or movement of the litter 14 withinthe chamber 24, the forward rotational force of the separating device 26then overcomes the opposite frictional and other forces to permit theseparating device 26 to begin rotation relative to the drum 18.Thereafter, the separating device 26 continues its rotation relative tothe drum 18 while the drum is relatively stationary.

If the frictional or adherent forces are not overcome by the rotatingseparating device 26 before position 104 a on drum 18 is turned by thelimited angular amount, the rotation of the drum 18 will be stopped by astop 106. The stop 106 may be a mechanical or electrical stop. The stop106 halts the rotation of the drum 18, but permits the separating device26 to continue its rotation thereafter. The stop 106 may be formedbetween the drum 18 and an outer, fixed housing 40 (FIG. 6A), or otherfixed member such as the base 16. After engagement of the stop 106, thedrum 18 may remain in place or may fall back to or toward its original,rest position. The separating device 26 can then more thoroughly siftthe litter 14 by its rotation relative to the drum 18.

The animal waste 12 is removed from the chamber 24 through theinitiation of a cleaning cycle. A typical cleaning cycle includes therotary drive 28 moving the separating device 26 within the chamber 24both concurrent with and relative to the cylindrical side wall 19 asdescribed above. The rotation permits the separating device 26 to siftthrough the litter 14 within the chamber 24 and remove the animal waste12 from the litter 14. Upon further rotation of the separating device26, the animal waste 12 is also removed from the drum 18 itself.

Referring to FIGS. 1-3, the drum 18 is preferably a cylindricalenclosure that includes a front opening 30 in the drum front wall 20that is sized to allow a domestic animal, such as a cat, to enter thechamber 24 in order to urinate or defecate depositing such waste 12 inthe litter 14. The drum also includes a rear opening 32 defined in thedrum rear wall 22 that is sized to receive the waste 12 and agglomeratesof waste 12 and litter 14 from the separating device 26 during thecleaning cycle to remove the waste 12 from the chamber 24. As has beenmentioned, while the chamber 24 is shown as being cylindrical, otherconfigurations may also be used so long as the separating device 26 isable to sift through the litter 14 and remove the waste 12 from thechamber 24.

As shown on FIGS. 1-2, a removable storage container 34 is mounted onbottom wall 16 a of the base 16 at the rear wall 22 of the drum 18. Thestorage container 34 communicates with chamber 24 through the rearopening 32 and a discharge chute 36 to receive the waste directedthrough the rear opening 32 by the separating device 26. In oneembodiment as shown on FIG. 2, the chute 36 is removable with thestorage container 34 to keep odors from leaking from the storagecontainer 34 (as explained in detail below) when the storage container34 is removed. Alternatively, the chute 36 is fixed to the drum 18 sothat only the storage container 34 is removable. In either instance, auser can remove the waste at any time or wait until the storagecontainer 34 is full while the litter 14 within the chamber 24 isautomatically kept clean.

In the preferred and illustrated form, the support for rotatablymounting the drum 18 is the base 16. Alternatively, the support for thedrum 18 can be rotary bearing assemblies such as including a centralrear axle extending out from the rear drum wall to be fixed to the outerhousing 40 or other fixed structure such as the motor 28, as will bedescribed hereinafter. In the illustrated from in FIGS. 1 and 6, thebase 16 has support fins 38 extending upward from the bottom wall 16 ato upper arcuate edges 38 a having substantially the same curvature asthe outer, cylindrical surface of the drum, with the fins aligned alongboth sides of the base 16 in order to avoid lateral shifting of the drum18 and to keep it in alignment with the separating device 26. It is alsocontemplated that the fins 38 may include wheels, bearings, or the liketo allow the drum 18 to rotate easily. Further, any engaging surfaces ofthe drum, base, and fins are preferably of low friction material forease of drum rotation.

Referring again to FIGS. 1-3, a removable housing 40 is provided toenclose the apparatus 10. The housing 40 includes a front wall 42, rearwall 44, and left and right side walls 46, 48 respectively; all fourwalls extend downwardly from a top wall 49. When covering the drum 18, abottom peripheral edge 50 of the housing 40 rests on the base wall 16 a.The housing 40 is preferably removable from the base 16 for cleaning,repair, or maintenance of the apparatus 10. The housing 40 is preferablymade of plastic, or any other material that traps the odors from thewaste 12 within the housing, and should be strong enough to at leastwithstand the impact of a small animal jumping on or pushing against it.

As best shown in FIG. 2, one embodiment of the apparatus 10 includes acut-out 51 in the housing 40 that extends along the rear and sidewalls44, 46 and 48 to align with a periphery 53 of the storage container 34so that a user can change the storage container 34 without the need oflifting the housing 40. The housing 40 need not include the cut-out 51so that it covers the storage container 34 and so that the housing 40must be lifted off the base 16 in order to empty the storage container34. Rather than cut-out 51, a partial cut-out may be provided so thatthe housing 40 covers most of the storage container 34 while exposingenough of the location reserved for the storage container 34 so that auser can quickly determine whether or not the storage container is inplace for operation.

As discussed previously, the chute 36 may be removable with the storagecontainer 34. In this case, the rear wall 44 and the right side wall 48would have a periphery 55 that corresponds to the shape of the chute 36as shown in FIG. 2. The chute 36 may also be separately removable fromthe housing 40 through the cut-out 51 either before or after the storagecontainer 34 is removed from the housing 40.

As illustrated in FIG. 1, the housing 40 includes a front opening 54 inthe front wall 42 in the shape of an arched doorway. The opening 54 issized so that the upper curved edge portion 54 a thereof is generallyaligned with the corresponding upper, curved portion 30 a of the chamberfront wall opening 30, and the parallel side edge portions 54 b have awidth therebetween corresponding to the diameter of the opening 30 inorder to permit the animal to pass through the housing 40 and into thechamber 24 without having to fit through a smaller or misaligned housingopening 54 relative to the chamber opening 30.

As best seen in FIG. 3, the chamber front end wall 20 has an outwardlyprojecting, circular flange 56 that extends about the chamber front wallopening 30. The housing 40 slides over the drum 18 so that edge portions54 a and 54 b fit between the flange 56 and the front end wall 20, tosecurely fit the housing 40 over the drum 18. The flange 56 provides asmoothly contoured surface at the edge of the front opening 54 toeliminate any rough or sharp edges that may scratch or otherwise injurethe animal as it enters the apparatus 10. It will be appreciated thatthe shape of the front openings 30 and 54 is not limited to thatdescribed as long as the openings permit an animal to enter theapparatus 10.

Referring again to FIG. 3, the drum 18 has a central, rotational Z-axis.Preferably, the front chamber opening 30 is coaxial with thelongitudinal Z-axis so that no matter what the rotational position ofthe drum 18, the opening 30 will always be located in the sameapproximate position relative to the bottom of the chamber 24 so thatthe opening 30 is always conveniently positioned for the animal.

Referring to FIGS. 3-5, the separating device 26 is preferably anauger-shaped structure, such as an elongate, generally helical blade orrake 58 that spirals along an inner surface 60 of the chamber side wall19 from the rear end wall 22 to the front end wall 20. The separatingdevice 26 has a first end 62 positioned adjacent the rear end wall 22and a second end 64 adjacent the front end wall 20. The first end 62 ofthe separating device 26 is spaced from the Z-axis along the rear endwall 22, and is connected to the rotary drive 28 via a coupling in theform of a radially extending drive bar 66. The drive bar 66 is in turnconnected to a rotatable drive shaft 68 extending out of the rotarydrive 28 and through rear end wall 22. As shown in FIG. 3, the rotarydrive 28 is mounted behind the rear end wall 22 so that the drive shaft68 extends into the chamber 24 coaxially with the Z-axis. It will beunderstood that the rotary drive 28 can be mounted to the rear wall 44of the housing 40 or have any other support structure between the rearwall 44 and the chamber rear end wall 22, as long as the drive shaft 68can extend into chamber 24 to rotate the separating device 26. In thisregard, the shaft 68 can serve as the previously-mentioned support axlefor the drum 18 with a rotary bearing fit in the rear opening 68 a ofthe end wall and through which the shaft 68 extends. In this instance,the motor 28 is mounted to the drum 18 and not the housing 40 so thatthe motor 28 stays with the drum 18 upon removal of the housing 40therefrom.

As the rotary drive 28 rotates the drive shaft 68, the drive bar 66turns to rotate or turn the separating device 26 about the Z-axis, alongthe chamber wall 19 and through the litter 14 residing in the chamber24. The second end 64 of the separating device 26 is free to move alongthe front end wall 20 or may be joined to an optional circular track orrotating plate (not shown) disposed on the front end wall 20.

Referring to FIG. 4, the separating device 26 is preferably formed froma reticulated structure, such as a screen, mesh, rake, or the like. Theseparating device 26 is preferably made of plastic, metal, or anymaterial that can withstand the forces necessary to sift through thelitter 14. Any structure is sufficient for the separating device 26 aslong as it has openings sized large enough to sift through the litter14, such as typical cat litter, but small enough so that solid animalwaste 12 and agglomerates will not typically fit therethrough. In oneconfiguration, the separating device 26 includes a plurality of elongaterails 70 that are curved and spaced to extend in parallel relationshipto each other for the length of the separating device 26 from end 62 toend 64. The rails 70 are attached by transverse, elongate supports 72. Aplurality of openings 74 are formed between the rails 70 and supports72, and the size and shape of the openings 74 may vary depending on thenumber, spacing, and size of the rails 70 and supports 72. It will beappreciated that the openings can be any shape as long as they are sizedto allow litter to pass therethrough while impeding the animal waste 12and clumped litter and agglomerates.

Referring now to FIGS. 4 and 5, the separating device 26 also includes aradially, outer edge 76 adjacent or engaged with the inner surface 60 ofthe chamber wall 19. Preferably, the outer edge 76 forms a scrapinginterface with the drum inner surface 60. That is, the outer edge 76preferably engages, or is closely spaced from, the inner surface 60while the separating device 26 rotates. Even if closely spaced from thedrum surface 60, at least some of the loose material of litter and/orwaste between the edge 76 and the surface 60 will scrape against thesurface 60 so that a scraping interface between the edge 76 and surface60 is still present during turning of the helical rake 26 in the drum18. Further, the friction developed at the scraping interface willassist in transmitting the rotary drive forces of the rake 26 to thedrum 18 for rotation thereof, as has previously been described. Inaddition, the scraping interface preferably keeps the amount of animalwaste 12 or litter 14 that can pass between the outer edge 76 and innersurface 60 to a minimum for increasing the efficiency of the cleaningcycle.

The outer edge 76 may be a different material than the remainder of theseparating device. For instance, the outer edge 76 may be formed from aresilient material such as rubber, or a more durable material such asnylon. In addition, the radially, outer edge 76 may also be one of therails 70, or as illustrated, a double rail 78 combined to form athicker, more durable edge.

As best seen in FIG. 6 the rear opening 32 is generally kidney-shapedand radially offset from the Z-axis. The arcuate rear opening 32 isgenerally disposed in an upper quadrant of the rear end wall 22, andgenerally corresponds with an entry opening 80 to the chute 36 so thatat least a portion of the arcuate discharge opening 32 is aligned withthe chute entry opening. As further described below, during a cleaningcycle the separating device 26 pushes animal waste 12 out the dischargeopening 32 in the rear end wall 22, through the entry opening 80 of thechute 36 for being guided into the storage device 34. Because the rearend wall 22 may rotate with the drum 18, the arcuate opening 32 extendsfor sufficient angular distance in a circumferential direction about theZ-axis, e.g., about 20 to about 180 degrees (preferably less than about90 degrees, such as 25 degrees), so that regardless of drum rotation,the rear opening 32 will at least partially overlap the entry opening80. In this manner, animal waste 12 fed through discharge opening 32will travel through chute opening 80 as well, for receipt in the storagecontainer 34. Optionally, the rear end wall 22 may also include varioussized and shaped openings 32, such as multiple openings, one largeopening and the like, so long as the rear chamber opening 32 partiallyoverlaps the entrance 80 at any position of the chamber 18. In analternative embodiment, the rear end wall 22 may be stationary (i.e. theback wall of the chamber is not attached to the drum side wall 19 and isinstead a part of the base or housing and substantially seals off therear end of the drum). In that case, the rear opening 32 need only matchthe shape of the entry opening 80 or be smaller and overlapped thereby.

Referring again to FIG. 6, the rear wall 44, the chute 36, and a sidewall 92 of the storage container 34 (best seen in FIG. 1) cooperate toenclose the rear of the apparatus 10 so that odors emanating from therear opening 32 cannot readily escape the housing 40, and waste at therear opening 32 will abut against the side wall 92 where the rearopening 32 extends beyond, above and/or below the entrance 80 of thechute 36. The housing 10 may have a back wall (not shown) that ispositioned between the side wall 92 of the storage container 34 and therear end wall 22 for the chamber 24.

Referring again to FIG. 1, the storage container 34 has a top rim 82extending about an opening 84 and shaped to correspond to, and engage, abottom rim 86 of the storage chute 36 for receipt of the animal waste 12therethrough. Since the storage container 34 and the chute 36 arepreferably removable from the apparatus 10, the apparatus 10 may alsoinclude a releasable connection 87 to secure the storage container 34 tothe chute 36. As shown, the releasable connection is a friction fitbetween the edges 86 and 82; however, the releasable connection 87 mayalso include VELCRO® straps, hook tabs in grooves, fasteners, or anyother device that secures the storage container 34 and/or chute 36 tothe apparatus 10 when in use but permits their detachment when necessaryto dispose of waste collected in the storage container 34, or to cleanthe storage container 34 and the chute 36. The container 34 may alsoinclude a detachable connection to the base 16 at one wall 16 a thereof.

The chute 36 guides the removed animal waste 12 from the chamber 24 tothe storage container 34. In order to keep odors from leaking from thestorage container 34, the chute 36 seals the top rim 82 of the storagecontainer 34, and the chute 36 has a pivoting door 88 mounted to theupper wall 36 a of the chute, in an upper hinge 90 to close the entryopening 80 on the chute 36 (FIG. 1). The door 88 pivots inwardly towardthe rear wall of the chute 36 when waste, transported by the separatingdevice 26, presses against the door 88. After the waste 12 falls throughthe chute 36, a biasing member such as a leaf or torsion coil spring,for example, closes the door 88 at the entrance 80 of the chute 36 andgenerally seals the storage container 34 to reduce the presence of odorsemanating from the apparatus 10.

Referring to FIG. 13, an alternative storage chamber 136 is illustrated.In this form, the storage chamber 136 includes a disposable chamber 138,such as a typical plastic storage bag, and a coupling tube 140 to couplethe disposable chamber 138 to the chute 36. The coupling tube 140preferably joins to the chute 36 in a manner similar to the previouslydescribed storage chamber 34 and directs the waste 12 from the chute 36into the disposable chamber 138 during a cleaning cycle. In theembodiment of FIG. 13, the disposable chamber 138 is joined to thecoupling tube 140 via an elastic member 142, such as a rubber band;however, the disposable chamber 138 may be fastened to the tube 140through other fastening methods such as hooks, loops, snaps, buttons,VELCRO®, tape, and the like. The alternative storage chamber 136 isadvantageous in that the chamber 136 requires minimal cleaning as thedisposable chamber 138 and any waste 12 contained therein are simplydisposed of when full and a new, empty disposable chamber 138 isattached to the chute 36 and tube 140 when needed.

Referring to FIGS. 6 and 6A, the drum 18 may be formed from twohalf-cylinder members 18 a and 18 b. A mating edge 94 of each piece 18a, 18 b is flared outwardly to form an edge flange 96 having a contactsurface 98. The contact surfaces 98 of each member 18 a and 18 b aresecured together as by welding or the like. The flanges 96 arepreferably elongated and substantially run the entire axial length ofthe drum side wall 19, although it will be appreciated that the flanges96 can be shorter or be discontinuous along the length of the drum sidewall 19 at any desired spacing.

The housing 40 of the apparatus 10 is dimensioned to be slightly largerthan the drum 18 to permit the drum 18 to rotate within the housing 40.Thus, as shown in FIG. 6, the inner width W of the housing 40 isslightly larger than the outer diameter D of the cylindrical side wall19 of the drum 18. In one embodiment, the width W of the housing 40 isset to be small enough so that the flanges 96 or any other protrusionextending outwardly from the drum side wall 19 will engage with an innersurface 100 of the housing 40 to form the previously mentioned stop 106.Therefore, the flanges 96 interfering with the housing 40 stops rotationof the drum 18, thereby preventing continued rotation of the drum 18past the stop 106.

More specifically, lower flanges 96 a can contact the inner surface 100of the left side wall 46 at position 104 a (shown in phantom in FIG. 6A)and the base 16, and specifically the fins 38 thereof, at position 104 c(FIG. 6) with the positions 104 a and 104 c being spaced byapproximately 25 degrees. In this manner, if the drum 18 rotates, it isallowed to rotate at most about 25 degrees between positions 104 a and104 c. Thus, the flanges 96 a and the inner surface 104 a cooperate toform the stop generally indicated as 106. Upper flanges 96 b, on theopposite side of the drum side wall 19 from the lower flanges 96 a,similarly engage with the housing side wall 48 and top wall 49 atdiametrically opposite positions, to positions 104 a and 104 c tocooperate to form stop 106.

While the stop mechanism 106 is described as a protrusion from the drumside wall 19 that engages with the housing 40, any stop that limits therotational motion of the drum 18 to a predetermined angular amount couldbe utilized. Thus, other stop mechanisms may be used such as having aprotrusion from the housing or other part of the apparatus 10 thatengages a surface or extension on the drum side wall 19. The stop mayalso be separate from the drum 18 and housing 40 or may be integral withboth or associated with only one of those structures. In addition, whilethe stop mechanism or device 106 is described as a mechanical stop usingthe flanges 96 and housing 40, the stop device 106 may also be manyother types of mechanical, electromechanical, or electrical stops, suchas solenoid devices, photoelectric eyes, limit switches, brakingdevices, and the like.

Referring to FIG. 1, the apparatus 10 may also include a variety ofmonitoring devices, such as sensors, to monitor various conditionswithin the apparatus 10. For instance, the apparatus 10 may include ananimal detection sensor 108 to detect when an animal enters and leavesthe chamber 24 in order to delay or initiate a cleaning cycle after theanimal has exited the drum 18. For example, the animal detection sensor108 may be a photo eye device 108 including a transmitter 108 a andreceived 108 b disposed on the housing front wall 42. The transmitter108 a projects a light beam across the opening 54 toward the receiver108 b. When the beam is broken by an animal entering or leaving the drum18 through the opening 54, the receiver 108 b will send a signal to acontroller 120 (FIG. 1) which controls operation of the rake motor 28.

In addition, the storage container 34 may also include a waste sensor110 to determine when the storage container 34 is full of animal waste12 and needs to be changed. A litter sensor 112 may also be placed inthe chamber 24 to monitor the quantity of litter within the chamber.Because it is not uncommon for typical cat litter to clump uponcontacting moisture or to stick to the animal waste 12, it is possiblethat litter 12 may also be removed from the chamber 24 during thecleaning cycle in agglomerates as has been described. As a result, thelitter sensor 112 would detect when a predetermined amount of litter 14has been removed from the chamber 24 after repeated cleanings to providea notification that more litter 14 may need to be added to the chamber24. As mentioned, the sensor 108 would send signals to the controller120 connected to the rotary drive 28 for controlling its operation, andthe sensors 110 and 112 can be operable to provide an audio or visualalert as appropriate when the container 34 needs to be emptied and thelitter needs to be refilled in the drum, respectively.

Referring now to FIGS. 7A,B through 11A,B and the flow chart of FIG. 13,the operation of the apparatus 10 and a typical cleaning cycle will bedescribed. The flowchart of FIG. 13 illustrates exemplary steps tocomplete a cleaning cycle in three different modes of operation: anautomatic mode, a manual mode, and a timed mode. In the automatic mode,after an animal, such as a cat, enters the chamber 24 and deposits aquantity of animal waste 12 therein, the apparatus 10 initiates acleaning cycle to remove the animal waste 12 from the litter 14. Thecleaning cycle may be delayed until the animal leaves the chamber 24(step 154), and then started automatically (step 156) when the sensor108 detects the absence of the animal from the chamber (step 152). Inthe alternative, the cleaning cycle may be initiated manually (step 157)by actuation of a switch or button (not shown) on the apparatus 10, suchas on the exterior of the housing 40 that sends a signal to the rotarydrive 28 or the controller 120 that controls the rotary drive 28. In thetimed mode, the cleaning cycle is initiated after a predetermined lengthof time has elapsed after the last cleaning cycle (step 159), such asonce per day. While three exemplary modes of operation of the apparatus10 are disclosed in FIG. 12, the cleaning cycle of the apparatus 10 mayalso be initiated via other functions, signals, sensors and operate inother modes.

Once initiated, the rotary drive 28 rotates the drive shaft 68, whichturns the drive rod 66 and the connected separating rake 26 within thedrum 18 (step 156). The rotary drive 28 drives the rake 26 so that therails 70, the supports 72, and the outer edge 76 of the separatingdevice 26 are driven into the litter 14 and then continuously moved androtated through the litter 14. The preferred helical, contoured shape ofthe separating device 26 permits the separating device 26 to siftthrough the litter to engage any waste 12 therein. The helical contourof the rake 26 scoops the waste and creates a forward-moving, sweeping,sifting and/or raking action on and through the litter 14 as itcontinues to be turned. As depicted in FIGS. 7A-7B, 8A-8B, and 9A-9B,this sweeping action moves any waste 12 on, or buried in, the litter 14in a direction from the front end wall 20 toward the rear end wall 22within the chamber 24. This sweeping action will also capture and movehardened clumps of litter 14 that agglomerated due to either the solidor liquid waste.

It will be appreciated that the separating device 26 can take on manydifferent forms as long as it can be attached to the rotary drive 28 andit is still able to sift through the litter so that the litter is freeto pass through it while the separating device 26 captures the waste 12.Thus, the separating device 26 may instead have more of a curvilinear orboxed scoop shape, or it may have other shapes, such as any curved,annular, penannular, or any other shape that can be rotated through thechamber 24 while performing the operations described herein. It iscontemplated that a non-helical, separating device may need othermechanisms to drive it through the chamber 24, such as a telescoping rodor other equivalent structure.

As illustrated in FIGS. 9A and 9B, as the separating device 26 continuesto rotate, the waste 12 is transported over or through the litter 14until the waste 12 abuts the rear end wall 22 (step 164). The separatingdevice 26 can be constructed so that any one point thereon willundertake 360 degrees of rotation with one full turn of the drive bar66.

Once the waste 12 has contacted the chamber rear wall 22, furtherrotation of the separating device 26 separates the waste 12 from thelitter 14, scooping the waste 12, and any adhering litter 14, in anupwardly direction along the rear end wall 22 towards the rear end wallopening 32, as illustrated in FIGS. 10A and 10B.

Referring to FIGS. 11A and 11B, when the waste 12 is lifted to where therear end wall opening 32 communicates with the entry opening 80 of thechute 36, continued rotation of the helical rake 26 pushes the waste 12against the door 88 so that it pivots open against its spring bias andthe waste is directed through the rear end wall opening 32 and the entryopening 80. At this point, the open door 88 and gravity allow the animalwaste 12 to drop into storage container 34 (step 164). The door 88 isbiased to close and seal the waste 12 within the storage container 34once the waste has passed through the chute 36.

The cleaning cycle may be stopped and the rotary drive 28 shut off viathe controller 120, after rotating the separating device 26 apredetermined duration (step 166), after the detection of an animalabout to enter the chamber 24, or after the detection of a full storagecontainer 34 (step 168). With this configuration, the apparatus 10 is aself-cleaning litter box that removes the animal waste 12 from thechamber 24 with minimal outside intervention by a user.

As discussed previously, the rotary drive 28 can directly rotate theseparating device 26 without the need to always first rotate thestructure that forms the chamber 24 holding the litter, in this case thedrum 18. In other words, when the separating device 26 is free to rotatewithin the drum 18, the rotary drive 28 does not need to continuouslyprovide enough torque to overcome the weight of the drum walls 19, 20and/or 22 as well as the weight of the litter 12. Therefore, the rotarydrive 28 has a reduced peak power or maximum horse power/torque ratingthat is significantly less than what would be needed to continuouslyrotate a drum 18 permanently fixed to the separating device 26.

As also discussed previously, in a further aspect of the invention, anon-permanent driving engagement between the separating device 26 andthe drum 18 may be formed so that the drum 18 rotates with the rotatingseparating device 26 for a short circumferential distance (step 158 andstep 160). This may occur due to friction forces at the scrapinginterface between the rake edge 76 and inner drum surface 60. Inaddition, the chamber wall 19 will also rotate when the litter 12adheres to the drum 18 due to agglomeration or other properties in thelitter 14 that make the litter 14 particularly adherent or difficult tosift through. The strength of the resulting adherent force in thissecond situation may depend on the amount and/or weight of the litter14, the position of the litter 14 within the chamber 24, the size andchemical properties of the litter grains, the type and amount of waste12 in the litter 14, and/or the moisture content of the litter 14.Herein the term “adherent force” simply means any force that adheres thelitter to both the separating device 26 and the drum wall 19 and mayitself include a frictional component.

In either of the situations described above that cause the drum 18 torotate with the separating device 26, these situations usually, but notalways, occur upon start-up of the cleaning cycle when the motion of theseparating device 26 is being initiated from a static state, when thelargest amount of torque and the peak power requirement occurs. It willbe understood, however, that the driving engagement between the rake anddrum may occur at any time, causing the drum 18 to intermittently startand stop rotation throughout a cleaning cycle as a result of theproperties of the litter 14, some of which were described previously,and which may affect the level of frictional and adherent forces betweenthe separating device 26 and the drum 18.

Once the drum 18 is rotating with the separating device 26, the drivingengagement will cease when the separating device 26 overcomes thefrictional force or adherent force that have the rake 26 driving thedrum 18 for rotation. In most cases, the rotation of the drum 18 and theseparating device 26 will shift the litter 14 enough to reduce thefrictional or adherent force so that the rotational force of theseparating device 26 and the opposite force resulting from the weight ofthe drum 18 and the litter 14 overcomes the reduced frictional oradherent force so that the drum 18 will cease rotating with the rake 26.With this operation, the rotary drive 28 does not need to overcome thefull frictional or adherent force that would occur if the chamber wall18 was fixed. As a result, it is believed the peak power requirements ofthe rotary drive can be maintained at about less than half of thatrequired by a configuration that uses a rotating sifting member in afixed, non-rotating drum 18.

Referring again to FIGS. 6 and 6A, if the frictional or adherent forcesare not overcome by the drive force applied to the rake 26, movement ofthe rake 26 relative to the drum 18 is caused by the stop device 106, asdescribed above, halting the rotation of the drum 18 while theseparating device 26 continues being turned therein. More specifically,when the chamber wall 18 rotates far enough so that its flanges 96 aand/or 96 b engage with the housing 40 (preferably a maximum of about180 degrees or less of circumferential rotation and most preferablyabout 25 degrees), the drum 18 no longer rotates in the same directionas the rotary drive force applied to the rake 26.

At this point, the rotational force from the separating device 26, andin turn from rotary drive 28, must overcome whatever adherent orfrictional force that has caused the chamber wall 18 to rotate this far.As mentioned above, this force should be reduced from the initial amountof force that caused the drum 18 to rotate. In addition, the engagementof the structure of stop device 106 may further shift the litter 14 andreduce the frictional or adherent forces.

With the stop device 106 ceasing further rotation of the drum 18, thedriving engagement between the rake 26 and drum 18 is broken. At thispoint without further drum rotation, the outer edge 76 of the rake 26scrapes along the inner surface 60 of the drum 18. In this instance,either the stuck litter 12 separates from the chamber wall 18 and/or theseparating device 26 is able to now easily sift through litter 14 it wasadhering to or pushing against.

After the separation, the drum 18 can either remain in place or canrotate back to its original, resting position. The separating device 26can then continue to sift the litter 14 with the drum 18 substantiallyremaining in place, although it should be noted that the drum 18, if ithas rotated back toward its initial rest position, may again be drivenfor rotation by the rake during the cleaning cycle.

After a cleaning cycle is complete, the rake 26 may have pushed aquantity of litter 14 towards the rear wall 22 of the drum 18, which mayleave the litter 14 unevenly distributed within the drum 18. As aresult, after the cleaning cycle is complete, the rotary drive 28 ispreferably rotated in reverse so that the rake 26 is also rotated inreverse a short distance within the drum 18 (Step 169). In this manner,the rake 26 will move any litter 14 that may have accumulated near therear wall 22 of the drum more evenly throughout the drum 18.

With the above-described arrangement, the rotary drive 28 can be smallerthan similar devices that continuously rotate a chamber and a siftingmember together, or devices that rotate a sifting member within a fixedchamber forcing the rotary drive to overcome the full frictional oradherent forces therein. This smaller rotary drive 28 is advantageous inthat the device 28 can be less costly, weighs less, is quieter, and ismore cost efficient to operate. As mentioned previously, a preferredrotary drive is a small 6 volt DC gear motor that operates on D-Cellbatteries generating less than 0.1 horsepower, and preferably, about1/50 horsepower.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modification will occur to those skilled in the art, and it isintended in the appended claims to cover all those changes andmodifications which fall within the true spirit and scope of the presentinvention.

1. An apparatus for removing animal waste from litter, the apparatuscomprising: a receptacle for holding litter therein; a sifting memberfor separating animal waste from the litter; a drive connected to thesifting member to be operable for shifting the sifting member throughthe litter in the receptacle so that operation of the drive does notdirectly cause the receptacle to move while the drive is operated toshift the sifting member through the litter in the receptacle; a supportfor the receptacle configured to allow the receptacle to move with thesifting member as an incident of the sifting member being shiftedthrough the litter so that the receptacle is only indirectly moved byoperation of the drive to reduce power requirements for the drive; and astop arranged to limit movement of the receptacle to a predeterminedamount so that the stop is operable to keep the receptacle from movingbeyond the predetermined amount while the drive is operated to continueto shift the sifting member through the litter in the receptacle.
 2. Theapparatus of claim 1 wherein the receptacle comprises a generallycylindrical drum, the drive comprises a rotary drive, and the siftingmember has a helical configuration that is turned in the drum by therotary drive for transporting the separated animal waste through thedrum.
 3. The apparatus of claim 1 wherein the receptacle has a generallycylindrical configuration so that the receptacle is a cylindricalreceptacle, the sifting member is a helical rake in the cylindricalreceptacle, the drive is a motor drive that turns the helical rake inthe cylindrical receptacle, and the predetermined amount of movement ofthe receptacle is a predetermined amount of rotation of the cylindricalreceptacle that is less than a full rotation thereof.
 4. The apparatusof claim 3 wherein the predetermined amount of rotation is less thanabout ninety degrees of rotation.
 5. The apparatus of claim 1 includingan outer housing in which the receptacle is disposed, and the stop isbetween the outer housing and receptacle.
 6. A method for separatinganimal waste from litter in a cylindrical receptacle, the methodcomprising: turning a separating device in a predetermined direction inthe cylindrical receptacle to move through the litter therein; allowingthe receptacle to move in the turning direction as the separating devicemoves through the litter for a limited angular distance to reduce powerneeded for turning the separating device; continuing turning of theseparating device after the receptacle has traveled through the limitedangular distance for separating animal waste from the litter andcarrying the waste through the cylindrical receptacle.
 7. The method ofclaim 6 wherein the separating device is turned by driving theseparating device with a motor.
 8. The method of claim 6 includingstopping the receptacle from further movement in the turning directionafter the receptacle has traveled through the limited angular distance.9. The method of claim 6 including turning the separating device in anopposite direction after carrying the waste through the cylindricalreceptacle.